It is sufficiently known to guy lattice booms in crane operation. The guying used as a rule runs over the boom back, with the guying being connected to the crane or to the boom at the respective end regions. To limit the deflection of booms on erection and during crane operation, it is already known to insert an additional guying device between the connection points of the guying, for example in the form of a further guying support over which the guying runs. Due to the angling of the guying caused by this, if the guying is loaded, an upwardly directed tensile force results in the additional guying device. This tensile force pulls the boom upward and thereby limits the total deflection of the boom system. The additional guying device has typically been designed as a rope construction or as light steel construction.
A schematic drawing of such a boom system using a lattice boom is shown in FIG. 1A A boom 1 is guyed by means of a guying 2. An additional guying support 3 that is installed in the central region of the boom 1 transmits a tensile stress applied by the guying 2 onto the boom 1 so that its deflection is limited in the region of the additional guying support 3. FIG. 1B illustrates the deflection of the boom without any additional guying support while FIG. 1C illustrates the deflection of the boom 1 limited by the guying support 3. The hatched lines 5, 6 show the possible deflection of the boom 1 during the erection or operation of the crane.
In the meantime, cranes or crane booms have become longer and longer in dimension, which results in greater deformations of the boom system in crane operation. An increasing problem here is the lateral deformation of the boom system by engaging transverse forces, e.g. by wind, slanted position, imperfections. FIG. 2 shows a rear view of the crane shows an example. The boom 1 is laterally deformed by the engaging transverse force FQ. The lateral deformation is additionally increased by attaching the load 100 to the lifting hook 101. The 2nd order theory plays a role here, i.e. the equilibrium at the deformed system is looked at. Forces that had no influence on the non-deformed system now have an influence. The boom 1 experiences displacement from its ideal alignment in the luffing plane 103 due to a slanted position α or due to a transverse load 102 such as wind. The guying 20 introduces a holding force into the boom 1; in addition, in accordance with the representation in FIG. 2, it introduces a further transverse force FQ, Absp. into the boom 1, which additionally increases the lateral deformation of the boom 1.
Bending moments furthermore occur at the boom system in crane operation, in particular with a slanted version of boom 1 and with an attached load. This is shown, for example, in FIG. 3A and FIG. 3B that show a crane configuration having a fixed tip (FIG. 3A) and having a luffable tip (FIG. 3B). A guying 2 extending from the derrick boom 4 to the boom tip simultaneously serves as a luffing drive of the boom 1. The behavior is comparable for both crane configurations. During crane operation with a slanted version of boom 1, high bending moments MB occur to the rear or upwardly in the region of the boom tip or of the upper part of the boom 1, which is indicated by the hatched surface. Conventional additional stay poles cannot counteract this bending moment since only a tensile force can be introduced by them into the boom system, i.e. the bending moment is theoretically further increased. For this reason, the additional guying support 3 are frequently only used during erection.
The object of the present invention comprises providing an improved guying of a boom that in particular makes larger payloads possible in crane operation.